arr.php

<?php

// Assuming https://wiki.php.net/rfc/arrow_functions makes it into PHP core, we can do this:

class Arr extends ArrayObject
{
    static function make($array)
    {
        return new self($array);
    }
 
    function map($func)
    {
        $res = new self();
        foreach ($this as $k => $v)
            $res[$k] = $func($k, $v);
        return $res;
    }
 
    function filter($func)
    {
        $res = new self();
        foreach ($this as $k => $v)
            if ($func($k, $v))
                $res[$k] = $v;
        return $res;
    }
}

$nums = Arr::make([10, 20, 30, 40])

return $nums->filter( fn($v) => $v > 15 )->map( fn($v) => $v * 2 );
// Additionally, also there's this:
$x = rand(3,6);
return $nums->filter( fn($v) => $v > 15 )->map( fn($v) => $v * 2 + $x );